1. Field of the Invention
Embodiments of the invention relate to the field of network communication, and more specifically, to virtual local area network (VLAN) stacking.
2. Description of Related Art
Ethernet is the most widely deployed Local Area Network (LAN) technology in the world today. Virtual Local Area Network (VLAN) is an Ethernet service defined in the Institute of Electrical and Electronics Engineers (IEEE) 802.1Q standard. The IEEE 802.1Q standard adds four additional bytes to the standard IEEE 802.3 Ethernet frame and is referred to as the VLAN tag. Q-in-Q is an IEEE 802.1ad standard, also known as VLAN stacking, provides a second VLAN tag, sometimes called the Provider tag, which is prepended to each customer packet. A VLAN tag field is 4 bytes long, but only 12 bits may be used for VLAN information. When used to support an Ethernet Service Unit (ESU) ring, 12 bits in an outer VLAN tag may be insufficient to contain all the packet forwarding information required in the ESU ring.
Existing techniques to solve the problem have a number of drawbacks. One technique uses the Medium Access Control (MAC)-in-MAC encapsulation as defined by the IEEE 802.1ah standard. However, this technique typically requires high-end Ethernet switch processors which may be too expensive for ESU edge boxes. Another technique may use proprietary solutions. However, this technique requires all equipment in an ESU ring to be constructed using components from proprietary sources.